Aerosol containers for containing and dispensing of fluid materials are well known and widely used. Products sold in aerosol containers include, for example, foods such as whipped cream; toiletries such as shaving cream, deodorant and hair spray; and paints, just to name a few. Dispensing is accomplished with the aid of a propellant under pressure. Aerosol containers offer the advantages of convenience and nearly complete dispensing of the fluid product material from the container. Disadvantages of aerosol container include their limited operating temperature range and the fact the container must be held upright to dispense properly.
A major concern over aerosol containers is the fact that the propellants used and the pressures required present environmental hazards. Aerosol cans fall into one of two categories as follows: 1) where the product and the propellant mix, which is a standard aerosol container and 2) where the product and the propellant are kept separated and that is known as a barrier pack. One of the concerns that exists with the barrier pack container is that propellant is locked into the container after the product has been expelled, creating an extreme hazard in the incineration of that type of container because a cloud of propellant can be formed if too many containers are crushed at the same time creating an explosive situation. A point of fact is that the Recycle Energy plant in Akron, Ohio has had several explosions due to too many of the barrier pack aerosols being crushed prior to incineration.
One of the principal classes of propellants are the fluorocarbons and chlorofluorocarbons (CFCs). Recent environmental concern regarding the use of these materials, and particularly the harmful effect on the ozone layer of the upper atmosphere, has prompted a search for replacement. In fact, some major manufacturers of these materials have pledged to phase out their production over the next decade or so. Another class of propellants are hydrocarbons, particularly the liquified petroleum gas (LPG) hydrocarbons such as butane and pentane. While these do not tend to deplete the ozone layer (as far as is known), they do present other hazards because of their flammability. Also, there are certain hazards in filling, transporting, storing and incineration of aerosol containers because of the high pressure required, no matter what propellant is used. These hazards are reflected in terms of costs, e.g., safety precautions in filling and handling, insurance costs, etc.
Self-pressurized containers have been suggested as an alternative to aerosol containers. Representative self-pressurized containers include those shown and described in U.S. Pat. No. 4,387,833 to Venus, Jr. and 4,423,829 to Katz. These references, which are rather similar in their teachings, describe apparatus for containing and dispensing of fluids under pressure in which no propellant is used and in which the fluid material to be dispensed is contained in a flexible plastic liner which in turn is contained in (from the inside out) a fabric sleeve and an elastomeric sleeve, which surround the liner except for a small neck portion at the top. The liner (except for the neck portion) has a plurality of longitudinally extending folds. When the liner is filled under pressure with the desired product, the entire assembly expands radially. The liner, which has a star shaped configuration when folded and not under pressure, is nearly circular in cross section when fully expanded. The elastomeric sleeve stores energy as a result of its radial expansion. This stored energy in the sleeve causes fluid to be dispensed upon opening of the dispensing valve. The container assembly contracts radially and the liner becomes folded, as it is emptied.
A disadvantage of self-pressurized containers of this sort is that an appreciable quantity of product remains inside the liner when it has been emptied as far as possible. This, of course, is costly. This may be attributable to the fact that the liners in the Venus and Katz structures are formed (e.g., by blow molding) in a smooth, essentially cylindrical configuration, and the folds or creases are then formed afterward. Since the preferred plastic materials have "memory", the liner seeks to return to the shape in which it is formed and resists becoming completely folded, which is essential to substantially complete expulsion of the product.
A further disadvantage of the Venus and Katz structures lies in the valve assembly at the top of the container. In this valve assembly, a cylindrical wall of a valve body is joined solely to the neck portion of the liner, with no additional support structure.
The neck portion of the liner is made thicker than the rest of the liner and is designed to use only one valve assembly.